Canon Speedlite 430EX II is the second incarnation of the popular Canon Speedlite 430EX. This flash is a Mark II and not the next generation model, which carries no major improvements. The flashes are pretty much alike.
Below is the list of new features offered by Canon Speedlite 430EX II flashgun:
The rest (head, body, buttons, etc.) is almost identical. So, the decision on which one to get really depends on the price difference and whether the new features look attractive to you to justify the extra cost. If you go with the Speedlite 430EX II, make sure you are OK with the absence of dedicated wireless mode switch.